Biased pivot assembly



Sept. 27, 1966 .G. w. KNECHT BIASED PIVOT ASSEMBLY Filed April v, 1964 #NWN IN V EN TOR.

m mJy L M iw i vz B ATTORNEY United States Patent O "ice 3,275,965 BIASED PIVT ASSEMBLY George W. Knecht, Brooklyn, NX., assignor to Murray Manufacturing Corporation, Brooklyn, N.Y., a corporation of New York i Filed Apr. '7, 1964, Ser. No. 357,877 7 Claims. (Cl. 335-276) This invention relates to a novel pivot assembly in which the pivoting member is always rotationally biased in the same direction regardless of the attitude of the assembly.

In applications too numerous to mention, it is necessary to bias an angularly displaceable member to ensure its return to a home position upon the removal of a latch or force maintaining the member in a position to which it has been urged. Conventional arrangements employ a spring, between the member and a fixed adjacent surface,

'for this purpose. However, it is apparent that if an arrangement could be devised which would obviate the necessity of utilizing a spring, a saving in both cost and space would arise.

Accordingly, it is the object of this invention to pivotally bia-s an angularly displaceable member without the necessity of employing an exterior force.

It is a further object of this invention to provide an arrangement which will satisfy the aforementioned object regardless of the attitude of the housing in which the member is disposed.

Briefly, the invention is predicated upon the concept of employing a pivotal member having a defined neck portion in conjunction with a pivoting member having an aperture disposed at its center of gravity and embracing the neck portion of the pivotal member, and means at the neck-aperture intersection for providing a pair of pivots, the operational one of which is always offset on the same side of the center of gravity of the pivoting member, regardless of the assembly attitude.

The above mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will best be understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings wherein:

FIG. l is an exploded perspective of the pivot assembly according to the invention;

FIGS. 2(a)-2(d) illustrate the biasing forces present in each of four assembly attitudes;

FIGS. 3 (a) and 3 (b) are front elevation and side crosssectional views, respectively, for illustrating the effect of inclining the pivotal members neck portion; and

FIG. 4 shows the invention embodied in the magnetic circuit of an electromagnet.

Referring now to the figures, and in particular to FIG.

l, there is shown a pivoting member A and a pivotal member B in exploded relationship. The letters with the numeric subscripts (A1, A2, B1, and B2) denote the ends of the associated members for later reference with respect to FIGS. 2(a) through 2(d).

The pivoting member A contains a defined aperture passing through its body at a location which will centrally encompass the center of gravity CG. The precise shape of the aperture is most simply defined by considering the surfaces resulting from an intersection of the member A with a right-parallelepiped RP (i.e. a parallelepiped, all of whose surfaces are rectangles) entering at an angle a to the surface.

The pivotal member B comprises a neck portion N-N which in the assembled form (see FIG. 3(b)) is disposed within the pivoting member aperture. Parallel flanges Pl-Pl and Pz-Pz, which are longitudinally spaced by an 3,275,965 Patented Sept. 27, 1966 amount exceeding the pivoting member thickness, retain the latter within the confines of the neck portion. These flanges are inclined at an angle with respect to a line drawn parallel the longitudinal axis of the neck, for a purpose that will become apparent when reference is made to the succeeding figures. Finally, a dovetail DT is provided, extending from the initial neck portion to the end B1, and including camming surfaces CS and CS' for facilitating the insertion of the pivotal member in the pivoting member aperture.

FIGS. 2(a) through 2(d) show the pivot assembly in four sequential attitudes, each rotated with respect to the preceding figure. In these figures it may be seen that because of the aperture and flange inclined surfaces, two pivot points PP and PP (which are actually edges extending into the paper) are formed. Since, however, gravity acts uniformly downwardly only one pivot point PP, is effective. Since the effective pivot point always appears to the right of the center of gravity CG, the latter, acting through moment arm MA, effects a counterclockwise bias on the pivoting member regardless of attitude. The result of this bias is shown by the dashed line in FIG. 2(a).

The foregoing description has been idealized to the extent that it was assumed that the housing containing the pivot assembly would be disposed in such a manner that the assembly would take one of the attitudes shown in FIGURES 2(a)2(d); i.e., with the pivoting member parallel or perpendicular the gravitational vector. Wherehowever, the housing may take any attitude, it will be appreciated that because of friction some intermediate positions exist in which a clear definition of the effective pivot point does not occur. In -order to obviate this possibility, the neck portion of the pivotal member may be slightly modified as shown in FIGS. 3(11) and 3 (b). Here the neck portion is made to vary linearly in width as it progresses longitudinally of the aperture. The resultant forces produced by the thus effected pair of inclined planes, particularly the component acting to the left, ensures the proper pivot point will control.

FIG. 4 shows the invention embodied in the magnetic circuit of an electromagnet EM; the pivoting and pivotal members constituting the movable and stationary armatures, respectively. The arrangement depicted is one which might be embodied in, for example, a circuit breaker. The pivoting member is provided with a lanced lip LL for latching a pivoted trip lever TL against a force F (resulting from a trippable assembly, not shown). On overload the electromagnet EM closes the air gap AG, lifting the lanced lip and thus releasing the trip lever. Since the electromagnet is in series with the load, the current ceases to traverse the coil. The pivot bias of the invention now returns the movable armature to the home position (that shown) where it may subsequently be cammed upwardly by the trip lever as it resets, dropping down (again by the effected bias) when the trip lever clears the lip LL to relatch the lever against the force F.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only -by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. A biased pivot assembly comprising the combination of a pivotal member having a defined neck portion, a pivoting member having an aperture disposed at the center of gravity thereof and embracing therein the neck portion of said pivotal member, and means at the neckaperture intersection for providing a pair of pivots offset on either side of the said center of gravity, the effective one of which is always on the same side regardless of the assemblys attitude.

2. A biased pivot assembly comprising the combination of a pivoting member having an aperture at the center of gravity defined by the surfaces resulting from an intersection with said member of a right-parallelepiped at an acute angle a; and a pivotal member having a neck portion passing through said aperture and including on each side of said neck portion a pair of parallel planar flanges spaced by an amount exceeding the pivoting member thickness at the aperture and inclined at an acute angle to a line drawn parallel the longitudinal axis of the said neck.

3. The assembly claimed in claim 2 in which az.

4. The assembly claimed in claim 2 in which said neck portion is formed adjacent one end of the pivotal member, said end up to and including said neck portion being dovetailed for squeezable insertion of said member into said pivoting member aperture.

5. The assembly claimed in claim 4 in which said neck portion is of rectangular cross-section increasing linearly in width as said neck progresses longitudinally towards said end.

6. An electromagnetic circuit comprising an electromagnet, and a biased armature assembly in series with said electromagnet in said magnetic circuit, said armature assembly comprising the combination of a pivotal member having a dened neck portion, a pivoting member having an aperture disposed at the center of gravity thereof and embracing therein the neck portion of said pivotal member,l and means at the neck-aperture intersection for providing a pair of pivots offset on either side of the said center of gravity, the effective one of which is always on the same side regardless of the assemblys attitude.

7. An electromagnetic circuit comprising an electromagnet, and a biased armature assembly in series with said electromagnet in said magnetic circuit, said armature assembly comprising the combination of a pivoting member having an aperture at the center of gravity defined by the surfaces resulting from an intersection with said memy'ber of a right-parallelepiped at an acute angle a; and a pivotal member having a neck portion passing through said aperture and including on each side of said neck portion a pair of parallel planar anges spaced by an amount exceeding the pivoting member thickness at the aperture and inclined at an acute angle to a line drawn parallel the longitudinal axis of the said neck.

References Cited by the Examiner UNITED STATES PATENTS 2,021,061 11/1935 Hedman 308-2 MILTON KAUFMAN, Primary Examiner. 

1. AN ELECTROMAGNETIC CIRCUIT COMPRISING AN ELECTROMAGNET, AND A BIASED ARMATURE ASSEMBLY IN SERIES WITH SAID ELECTROMAGNET IN SAID MAGNETIC CIRCUIT, SAID ARMATURE ASSEMBLY COMPRISING THE COMBINATION OF A PIVOTAL MEMBER HAVING A DEFINED NECK PORTION, A PIVOTING MEMBER HAVING AN APERTURE DISPOSED AT THE CENTER OF GRAVITY THEREOF AND EMBRACING THEREIN THE NECK PORTION OF SAID PIVOTAL MEMBER, AND MEANS AT THE NECK-APERTURE INTERSECTION FOR PROVIDING A PAIR OF PIVOTS OFFSET ON EITHER SIDE OF THE SAID CENTER OF GRAVITY, THE EFFECTIVE ONE OF WHICH IS ALWAYS ON THE SAME SIDE REGARDLESS OF THE ASSEMBLY''S ATTITUDE. 